Image processing apparatus and image processing method

ABSTRACT

An image processing apparatus for embedding predetermined information in an image includes an input unit for inputting the image, a division unit for dividing the input image into plural image regions, a periodicity generation unit for generating plural different periodicities, an addition unit for adding a predetermined value to a pixel value of each pixel in the image region divided by the division unit, on the basis of the periodicity, and a selection unit for selecting the periodicity for the addition from among the plural periodicities, in accordance with the predetermined information. Thus, image quality deterioration is reduced and an extraction error ratio at a time of extracting additional information is also reduced in a method of embedding the additional information in the image.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image processing apparatus and animage processing method.

2. Related Background Art

Conventionally, it has been actively studied to multiplex, in imageinformation, other information concerning an image represented by theimage information.

In recent years, a technique so-called an electronic watermark techniqueis standardized. The electronic watermark technique is the technique tomultiplex, in the image information representing a photograph, apainting and the like, additional information representing its author'sname, license and the like so that it becomes difficult to visuallydistinguish the additional information, and to circulate the multiplexedinformation through a network such as the Internet or the like.

As general methods of embedding the additional information, theelectronic watermark technique provides two methods, that is, one ofembedding the additional information in real space, and the other ofembedding the additional information by using a frequency band.

The simplest method of embedding the electronic watermark in real spaceis the method of decomposing the image information into bit planes, andallocating the bit plane of LSB (least significant bit) as the bit planeof the additional information.

Besides, in the method of embedding the additional information by usingthe frequency band, orthogonal transformation such as Fouriertransformation, discrete cosine transformation, wavelet transformationor the like is used. In any case, there is the method of embedding theadditional information by changing a transformation coefficient of aspecific band with use of a high frequency band which is difficult to bevisually remarkable or low and middle frequency bands which aredifficult to be influenced by quantization of the transformationcoefficient in data compression. Moreover, there is the electronicwatermark method that resistance to attack is hardened by using spectrumdiffusion.

These conventional methods as above are explained in detail in KineoMATSUI “Basic of Electronic Watermark”, Morikita Publishing Company,August 1998.

However, there are following problems in these conventional methods.

That is, the conventional method of embedding the electronic watermarkpremises that it is used on an electronic file.

FIG. 11 is a diagram showing additional information embedding which isgenerally performed in the electronic watermark technique, that is,image information A and additional information B are multiplexed by anaddition unit 1101 to generated multiplexed information C. Incidentally,FIG. 11 shows an example that the additional information is multiplexedin the real space region of the image information. If it is possible tocirculate the multiplexed information C without various image processessuch as filtering and the like and various encoding such as unreversiblecompression and the like, the additional information B can be easilydecoded from the multiplexed information C even in the conventionaltechnique. If the image information circulated on the Internet has acertain level of noise resistance, the additional information B can bedecoded even if digital filtering to improve image quality such as foredge emphasis, smoothing and the like is performed.

However, it is assumed that the multiplexed image information is printedby an output apparatus such as a printer or the like and the additionalinformation is captured from such a printed image, and moreover, it isassumed that print output is performed by using the printer merelyhaving expressive power of about two to several gradations for eachcolor. In recent years, although an ink-jet printer which can expressseveral gradations for each color by using ink of low-density dye andvariably controlling output dot diameters is available, the gradation ofa photographic image can not be expressed as long as a pseudo-gradationprocess is not performed.

That is, on the premise that the multiplexing method using theelectronic watermark technique shown in FIG. 11 is applied to theprinter output, as shown in FIG. 12, the multiplexed information C isconverted into quantized information D through a pseudo-gradationprocess 1201 and then printed on a paper through printer output 1202,whereby the multiplexed information C is changed to on-paper information(printed image) E having deteriorated image quality. Therefore, todecode the additional information from the on-paper information is todecode the additional information B from the on-paper information Eafter a series of processes in FIG. 12 is performed. Incidentally,information change amounts by the processes 1201 and 1202 are remarkablylarge, whereby it is very difficult to multiplex the additionalinformation so that the multiplexed information can not be visuallydiscriminated and to correctly decode the multiplexed additionalinformation from the paper.

In the above method of embedding the additional information in the bitplane in real space, it is almost impossible to decode the embeddedinformation on the paper.

On one hand, as for this, even a method of changing a power value in aspecific frequency band is similar.

For example, Japanese Patent Application Laid-Open No. 7-123244 proposesa technique of multiplexing information by embedding additionalinformation in a color difference component of which sensitivity isvisually low and a high frequency band of a saturation component.

However, in this technique, each bit data is allocated to each specificband (or specific frequency band), and “1” or “0” is expressed accordingto whether or not a pattern should be added to the specific band.Besides, in decoding, a frequency component of the specific band isextracted, and “1” or “0” is discriminated according to a thresholdprocess.

In this method, there are the following problems.

Since the threshold process is performed to the absolute value of thepower, the decoding from the paper is easily influenced by noise.

In order to strengthen against the noise, it is necessary to perform themultiplexing strongly, whereby image quality deteriorates.

Since a pseudo-gradation process is performed at a later stage, there isa fear that the absolute value of the power deteriorates due tofiltering of the pseudo-gradation process.

In order to cause the paper to have resistance to rotation, a start bitis necessary in the specific band.

The process is complicated as a whole.

That is, as above, the method of discriminating “1” bit or “0” bitaccording to the magnification of the absolute value of the power in thespecific band has many problems.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made to solve the aboveproblems, and an object thereof is to provide an image processingapparatus and an image processing method capable of controlling imagequality deterioration due to embedding of information and easilyextracting the information from a paper.

In order to achieve the above object, the image processing apparatusaccording to the present invention is characterized by an imageprocessing apparatus which embeds predetermined information in an image,comprising: an input means for inputting the image; a division means fordividing the input image into plural image regions; a periodicitygeneration means for generating plural different periodicities; anaddition means for adding a predetermined value to a pixel value of eachpixel in the image region divided by the division means, on the basis ofthe periodicity; and a selection means for selecting the periodicity forthe addition from among the plural periodicities, in accordance with thepredetermined information.

Moreover, the image processing apparatus according to the presentinvention is characterized by an image processing apparatus which embedspredetermined information in an image, comprising: an input means forinputting the image; a division means for dividing the input image intoplural image regions; a periodicity generation means for generatingplural different periodicities; an addition means for adding apredetermined value to a pixel value of each pixel in the image regiondivided by the division means, on the basis of the periodicity; aselection means for selecting the periodicity for the addition fromamong the plural periodicities, in accordance with the predeterminedinformation; a conversion means for converting each pixel into a densitysignal for each coloring material; and a recording means for recordingthe density signal after the conversion by the conversion means, on aprinting medium, wherein the addition means performs the additionprocess to the information before the conversion by the conversionmeans.

Moreover, the image processing method according to the present inventionis characterized by an image processing method of embeddingpredetermined information in an image, comprising: an input step ofinputting the image; a division step of dividing the input image intoplural image regions; a periodicity generation step of generating pluraldifferent periodicities; an addition step of adding a predeterminedvalue to a pixel value of each pixel in the image region divided in thedivision step, on the basis of the periodicity; and a selection step ofselecting the periodicity for the addition from among the pluralperiodicities, in accordance with the predetermined information.

Moreover, the image processing method according to the present inventionis characterized by an image processing method of embeddingpredetermined information in an image, comprising: an input step ofinputting the image; a division step of dividing the input image intoplural image regions; a periodicity generation step of generating pluraldifferent periodicities; an addition step of adding a predeterminedvalue to a pixel value of each pixel in the image region divided in thedivision step, on the basis of the periodicity; a selection step ofselecting the periodicity for the addition from among the pluralperiodicities, in accordance with the predetermined information; aconversion step of converting each pixel into a density signal for eachcoloring material; and a recording step of recording the density signalafter the conversion in the conversion step, on a printing medium,wherein the addition process in the addition step is performed to theinformation before the conversion in the conversion step.

Other objects and the features of the present invention will be becomeapparent from the following specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the substantial part of an imageprocessing system according to the present invention;

FIG. 2 is a block diagram showing the substantial part of an additionalinformation multiplexing apparatus shown in FIG. 1;

FIG. 3 is a block diagram showing the substantial part of an errordiffusion means shown in FIG. 2;

FIG. 4 is a flow chart showing an operation procedure of a multiplexingprocess including a periodicity selection means;

FIG. 5 is a diagram showing an example of a block;

FIGS. 6A and 6B are diagrams showing examples of two kinds ofperiodicities to be added;

FIG. 7 is a block diagram showing the substantial part of an additionalinformation separation apparatus shown in FIG. 1;

FIG. 8 is a block diagram showing classification in an orthogonaltransformation block;

FIG. 9 is a block diagram showing the substantial part of an additionalinformation multiplexing apparatus according to the second embodiment;

FIG. 10 is a block diagram showing the substantial part of an additionalinformation multiplexing apparatus according to the third embodiment;

FIG. 11 is a block diagram showing an example of multiplexing in aconventional method; and

FIG. 12 is a block diagram showing the example of the multiplexing inthe conventional method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention will beexplained in detail with reference to the attached drawings. Here, itshould be noted that it is effective to have an image processingapparatus according to the embodiments mainly as printer driver softwareor application software in a computer of generating image information tobe output to a printer engine, and it is also effective to have theimage processing apparatus as hardware and software in a copyingapparatus, a facsimile apparatus, a printer main body or the like.

First Embodiment

FIG. 1 is a block diagram showing the structure of an image processingsystem according to the first embodiment.

In FIG. 1, each of numerals 100 and 101 denotes an input terminal, thatis, multiple-gradation image information is input through the inputterminal 100, and necessary additional information to be embedded in theimage information is input through the input terminal 101. Theadditional information is the information different from the imageinformation input through the input terminal 100, and may be, forexample, audio information, text document information, variousinformation concerning license, shooting date and hour, shooting place,a cameraman and the like with respect to the image input through theinput terminal 100, completely different image information, and thelike.

Numeral 102 denotes an additional information multiplexing apparatuswhich embeds the additional information in the image information so thatthe embedded information is difficult to be visually discriminated. Theadditional information multiplexing apparatus 102 also controlsquantization of the input multiple-gradation image information as wellas the multiplexing of the additional information.

Numeral 103 denotes a printer which outputs the information generated bythe additional information multiplexing apparatus 102, by using aprinter engine. Here, as the printer 103, various printers such as anink-jet printer, a laser beam printer and the like capable of expressinggradations by using a pseudo-gradation process are assumed.

The information on the printed image output by the printer 103 is readby a scanner 104, the additional information embedded in the printedimage is separated by an additional information separation apparatus105, and the separated information is output to an output terminal 101.

FIG. 2 is a block diagram showing the structure of the additionalinformation multiplexing apparatus 102 shown in FIG. 1.

In FIG. 2, numeral 200 denotes a color conversion unit which convertsthe input image information such as R, G and B brightness signals or thelike into signals to be managed in color space based on coloringmaterials such as recording inks and the like.

Numeral 201 denotes a block generation unit which segments or dividesthe image signal decomposed to each ink color, for each predeterminedregion. Here, the block generation unit 201 may segment the image signalinto rectangular block regions or block regions other than therectangular block regions.

Numeral 202 denotes a periodicity selection unit which selects specificperiodicity for each region segmented by the block generation unit 201,on the basis of the additional information input through the inputterminal 101.

Numerals 203 and 204 respectively denote a periodicity A generation unitand a periodicity B generation unit, and each of the units 203 and 204is selected by a switch 205 on the basis of the selection result of theperiodicity selection unit 202. Then, the selected periodicity is addedto the image signal by an addition unit 206.

Numeral 207 denotes a pseudo-gradation processing unit which performs apseudo-gradation process to the image information after it ismultiplexed for each color, converts the information to generatequantization levels of which the number is less than the number of inputgradations, and then expresses area gradation based on quantized valuesof plural pixels. Although a dither process, an error diffusion processand the like are possible as the pseudo-gradation process, it is assumedthat the error diffusion process is used in the present embodimentbecause this process can achieve excellent expressive power.

Numeral 210 denotes a control unit which is composed of a CPU 211, a ROM212 and a RAM 213. Here, the CPU 211 controls the operations and theprocesses of such components as described above in accordance withcontrol programs stored in the ROM 212, and the RAM 213 is used as theworking area for the CPU 211.

FIG. 3 is a block diagram showing the detail of the error diffusionprocess to be performed by the pseudo-gradation processing unit 207.Here, it should be noted that the general error diffusion process isdescribed in R. Floyd & L. Steinberg “An Adaptive Algorithm for SpatialGrayscale”, SID Symposium Digest of Paper, pp. 36–37 (1975).

Here, the error diffusion process that the quantization value is binarywill be explained by way of example, but the quantization itself is notlimited to the binary data, that is, multivalued data, ternary data andfour-value data may be managed in the quantization.

Numeral 300 denotes an addition unit which adds together an attentionpixel value of multiplexed information to which additional informationhas been added and an already-binarized quantization error diffused tothe peripheral pixel.

Then, a quantization threshold sent from a quantization conditioncontrol unit and the addition result to which the error has been addedare compared with each other by a comparison unit 301, and “1” is outputif the compared result is larger than a predetermined threshold, while“0” is output if other conditions are satisfied. For example, in case ofexpressing the gradation of the pixel with eight-bit accuracy, it isgeneral to express it by “255” being the maximum value and “0” being theminimum value. Here, it is assumed that dots (by ink, toner and thelike) are printed on a paper when the quantization value is “1”.

Numeral 302 denotes a subtracter which calculates an difference (i.e.,error) between the quantization result and the above addition result,and an error distribution operation unit 303 distributes the errors tothe peripheral pixels to which future quantization process is to beperformed. In this case, an error distribution table 304 experimentallyset based on relative distances to the attention pixel is previouslyprovided, and the errors are distributed on the basis of distributionrates described on the error distribution table 304.

The error distribution table 304 of FIG. 3 represents the errordistribution table of peripheral four pixels, but the present inventionis not limited to this.

Next, an entire operation procedure including the operation of theperiodicity selection unit 202 will be explained with reference to aflow chart shown in FIG. 4.

In a step S400, a variable i is initialized. Here, the variable i is thevariable for counting an address in the vertical direction.

In a step S401, a variable j is initialized. Here, the variable j is thevariable for counting an address in the horizontal direction.

Next, in a step S402, it is judged whether or not the coordinates of thevariables i and j representing the current processing address belong tothe region to which the multiplexing process should be performed.

Then, the multiplexing region will be explained with reference to FIG.5. FIG. 5 shows one image of which the number of horizontal pixels isrepresented by WIDTH and the number of vertical pixels is represented byHEIGHT. Here, it is assumed that the additional information ismultiplexed in this image. Blocks each of which is composed of lateral Npixels and longitudinal M pixels are generated and arranged from theupper left of the image set as the original point. In the presentembodiment, although the original point is set as the basing point, thepoint distant from the original point may be set as the basing point.Incidentally, when the maximum information is to be multiplexed in thisimage, the blocks each of which is composed of N×M pixels are arrangedfrom the basing point. That is, if it is assumed that the number ofblocks capable of being arranged in the horizontal direction is W andthe number of blocks capable of being arranged in the vertical directionis H, the following expressions (1) and (2) are satisfied.W=INT(WIDTH/N)  (1)H=INT(HEIGHT/M)  (2)where INT( ) represents the integer portion of ( ).

The number of surplus pixels which can not be divided in each of theexpressions (1) and (2) corresponds to the edge when the plural N×Mblocks are arranged and is thus positioned outside the coding andmultiplexing region.

In FIG. 4, if it is judged in the step S402 that the attention pixel nowbeing processed is within the multiplexing region, the additionalinformation to be multiplexed is read. Here, to simplify theexplanation, it is assumed that the additional information is expressedfor each bit by using an arrangement code[ ]. For example, if it isassumed that the additional information is the information of 48 bits,the arrangement code[ ] is given from code[0] to code[47] each of whichstores one bit.

In a step S403, the information in the arrangement code[ ] issubstituted for a variable bit.bit=code[INT(i/M)×W+INT(j/N)]  (3)

Next, it is judged in a step S404 whether or not the obtained variablebit is “1”. As described above, since each arrangement code[ ] storesthe information of one bit, the value of the variable bit is representedby “0” or “1”. Incidentally, if judged in the step S404 that thevariable bit is “0”, the flow advances to a step S405 to selectperiodicity A, while if judged that the variable bit is “1”, the flowadvances to a step S406 to select periodicity B.

Next, in a step S407, an addition process of the selected periodicity isperformed.

FIGS. 6A and 6B are diagrams respectively showing examples of theperiodicities A and B. In these drawings, it is assumed that one smallsquare corresponds to one pixel, a numeral in each square represents anaddition value, and the addition value of the blank square is 0. Thatis, addition of +α and −α is performed to the pixel value at apredetermined period of each of the periodicities A and B.

Only the direction of the periodicity shown in FIG. 6A is different fromthat shown in FIG. 6B, that is, the period in the horizontal directionand the period in the vertical direction are only mutually replaced.

Incidentally, it should be noted that each of FIGS. 6A and 6B shows theaddition period by using a table of 8×8 pixels. That is, even if thesize of the used table is not the same as that of a table of N×M pixels,it only has to use the existing table repeatedly.

Next, in a step S408, the variable j in the horizontal direction isincremented by one, and it is judged in a step S409 whether or not theincremented variable j is less than WIDTH being the number of horizontalpixels of the image. The above process is repeated until the number ofprocessed pixels reaches WIDTH. Besides, if the process in thehorizontal direction corresponding to the number (WIDTH) of horizontalpixels ends, the variable i in the vertical direction is incremented byone in a step S410, and it is judged in a step S411 whether or not theincremented variable i is less than HEIGHT being the number of verticalpixels of the image. Similarly, the above process is repeated until thenumber of processed pixels reaches HEIGHT.

By the above operation procedure, it is possible to add the periodicityaccording to the code of the additional information for each blockcomposed of N×M pixels.

The pseudo-gradation process in the error diffusion method depends onthe characteristic of the above error distribution table 304, butgenerally has a characteristic of a wide-band high-pass filter. For thisreason, if the information is added in the same low and middle frequencybands that only the directions of the periodicities are changed as shownin FIGS. 6A and 6B, the power of the band where the information is addedis slightly interrupted by the error diffusion filter, but the power canbe attenuated almost uniformly. In other words, it is desirable todesign the process as paying attention to the following points.

In the plural periodicities to be generated, only the directions thereofare different from others.

The table which has the almost uniform characteristic of no anisotropy,as the filter interruption characteristic by the distribution table inthe error diffusion method, is used.

Moreover, with respect to how the power of the band where theinformation is added remains on the paper, the amplitude value a isexperimentally determined in optimization of the image quality.

Next, the additional information separation apparatus 105 will beexplained.

FIG. 7 is a block diagram showing the structure of the additionalinformation separation apparatus 105.

In FIG. 7, numeral 700 denotes an input terminal through which theinformation read by the scanner is input. Here, it should be noted thatthe resolution of the used scanner is preferably equal to or higher thanthat of the printer of producing the printed image. In order toaccurately read the dotted information of the printed image, it is ofcourse necessary that the resolution on the scanner side is twice ormore the resolution on the printer side in accordance with a samplingtheorem. However, if the resolution on the scanner side is equal to orhigher than the resolution on the printer side, the dotted informationcan be distinguished to some extent though it is not accurate. In thepresent embodiment, to simplify the explanation, it is assumed that theprinter resolution is the same as the scanner resolution.

Numeral 701 denotes a geometric displacement detection unit whichdetects geometric displacement (or aberration) of the image inputthrough the scanner. Here, there is of course a case where the imageinformation sent from the scanner through the input terminal 700 isgeometrically and greatly displaced from the image information beforethe printer output because it passes the various processes, whereby thegeometric displacement detection unit 701 detects the four edge pointsof the region where the image information of the printed image isassumed to be printed. Here, if the printer resolution is the same asthe scanner resolution, the rotation direction (oblique direction) ofthe image due to oblique paper feed on the printer, displacement (oraberration) at a time of setting the document on the scanner, and thelike is the great factor to be corrected. Thus, it is possible bydetecting the four edge points to discriminate how the displacementoccurs in the rotation direction.

Numeral 702 denotes a block generation unit which generates the blockseach composed of P×Q pixels. Here, this block should be smaller than theblock composed of N×M pixels generated in the multiplexing. That is, thefollowing relation should be satisfied.P≦N and Q≦M  (4)

Moreover, when the blocks each composed of P×Q pixels are generated,they are skipped at certain constant intervals. That is, these blocksare generated so that one block composed of P×Q pixels is included inthe region assumed to be the blocks each composed of N×M pixels at atime of multiplexing. The number of pixels to be skipped is basicallythe horizontal N pixels and the vertical M pixels, but it is necessaryto correct it by calculating a displacement amount for each block andadding the calculated displacement amount to the number of skippedpixels. Here, the displacement amount for each block is calculated bydividing the displacement amount detected by the geometric displacementdetection unit 701 by the number of blocks.

Numeral 703 denotes an orthogonal transformation unit which performsorthogonal transformation to the P×Q pixels given as the block. Here, itshould be noted that, at a time of performing the two-dimensionalorthogonal transformation, it is necessary to generate the blocks by thesquare block of Q=P. In the present embodiment, DCT (discrete cosinetransform) will be explained by way of example.

A transformation coefficient of the two-dimensional DCT for the blockcomposed of P×P pixels is given as follows.

$\begin{matrix}{{{F\left( {u,v} \right)} = {\left( {2/P} \right){C(u)}{C(v)}{\sum\limits_{n = 0}^{p - 1}{\sum\limits_{m = 0}^{p - 1}{{f\left( {n,m} \right)}{\cos\left( {\left( {{2n} + 1} \right)u\;{\pi/2}P} \right)}{\cos\left( {\left( {{2m} + 1} \right)v\;{\pi/2}P} \right)}}}}}}{{{\text{where}\mspace{14mu}{C(x)}} = {{1/\sqrt{2}}\mspace{14mu}\left( {x = 0} \right)}},{{C(x)} = {1\mspace{14mu}\left( {x \neq 0} \right)}}}} & (5)\end{matrix}$

Numeral 704 denotes a classification unit which performs classificationfor each band of the orthogonal transformation coefficient. FIG. 8 showsan example of the classification in case of P=Q=16, and also shows theorthogonal transformation coefficients F(u, v) within one block. In FIG.8, only the upper left component is a DC component, and the remaining255 components are AC components. Here, two classes, i.e., a class Abased on the coefficient F(4, 8) and a class B based on the coefficientF(8, 4), which are respectively indicated by the heavy lines in FIG. 8are formed. Such a classification means does not need to perform theclassification for all the 256 components, and it only has to performthe classification for the several classes based on the desiredcomponents. Here, it should be noted that the number of necessaryclasses corresponds to the number of periodicities added in themultiplexing, that is, the number of necessary classes does not exceedthe number of periodicities added in the multiplexing.

Numeral 705 denotes a power comparison unit which compares the summationof power of each class with others. To achieve a high-speed operation,the absolute value of the generated transformation coefficient can beused as substitution of the power. The signal of the additionalinformation is discriminated by comparing the summation of the power ofeach class with others.

Here, the example that the periodicities A and B respectively shown inFIGS. 6A and 6B are added in the multiplexing will be explained. Asdescribed above, the quantization based on the pseudo-gradation afterthe periodicities A and B are added greatly depends on the addedamplitude value a, but texture that the dots are arranged respectivelyin the different-angled oblique directions is easily generated. That is,in the block to which the periodicity A is added, great power isgenerated in the class A of FIG. 8 if the orthogonal transformation isperformed.

On the other hand, in the block to which the periodicity B is added,great power is generated in the class B of FIG. 8 if the orthogonaltransformation is performed. That is, by relatively comparing the powerin the class A with the power in the class B, it is possible todiscriminate which of the periodicities A and B the periodicity added inthe multiplexing of the corresponding block is. Since the periodicity islinked with the code of the additional information (i.e., bit in theexpression (3)), to be able to discriminate the kind of periodicityrepresents to be able to specify the multiplexed code.

In the example of the flow chart shown in FIG. 4, since bit=0 is set asthe periodicity A and bit=1 is set as the periodicity B, it is possibleto discriminate that bit=0 if the power in the class A is larger andbit=1 if the power in the class B is larger.

The present embodiment shows the example that the periodicities to beadded in the multiplexing are two, i.e., the periodicities A and B, andalso the classifications in the separating are two, i.e., the classes Aand B. Although this corresponds to the case where the additionalinformation in the block is one bit, three or more classifications canbe of course achieved by controlling more kinds of periodicities.

In the present embodiment, it is unnecessary to embed the information byperforming the orthogonal transformation in the multiplexing as in theconventional art. That is, aberration of the frequency after thequantization is generated only by adding the different periodicities.Moreover, since the deviation of the frequency is caught up in thegeneration of the high-frequency component in the error diffusionmethod, the deviation is not visually detected easily.

As above, in the present embodiment, the more the geometric displacementbecomes larger, the more the block-generated image becomes oblique,whereby the obtained frequency is aberrated from the desired frequency.For example, even in the case where the multiplexing is performed sothat the large power is generated by the coefficient F(4, 8), if theimage is oblique, the generated frequency is of course displaced fromthe coefficient F(4, 8). For this reason, it is possible to structurethat the classification is dynamically changed based on a geometricdisplacement amount. Of course, if the displacement amount is small, oneclass may be composed of only one component in the classification.

Moreover, the present embodiment shows the periodicities A and B and theclasses A and B by way of example, but the present invention is notlimited to them, that is, other periodicities are applicable. Moreover,the periodicity may be added without using the table, but by using acounter, by changing the horizontal and vertical periods.

Moreover, although the binarization is explained as an example of thequantization in the present embodiment, the present invention is notlimited to this.

Moreover, although the DCT is explained as an example of the orthogonaltransformation, the present invention is not limited to this. That is,other orthogonal transformation such as Hadamard transformation, Fouriertransformation, wavelet transformation or the like may be of courseused.

Second Embodiment

FIG. 9 is a block diagram showing the structure of an additionalinformation multiplexing apparatus according to the second embodiment.

The feature of FIG. 9 is to locate a color conversion unit 200 at thesubsequent stage of an addition unit 206. That is, in the firstembodiment shown in FIG. 2, after the input information such as the R(red), G (green) and B (blue) information is converted into theinformation representing ink colors of Y (yellow), M (magenta), C (cyan)and K (black), the periodicity is added for each ink color to achievethe multiplexing. On the other hand, in the present embodiment shown inFIG. 9, the periodicity is directly added to R, G and B brightnessinformation to achieve the multiplexing.

In the present embodiment, a multiplexing process is completed in thesame color space as that for the input image information, whereby theinformation obtained after the multiplexing can be again used forstorage, circulation and the like as an electronic file.

That is, the multiplexing information obtained at the subsequent stageof the addition unit 206 can be used as an image file in which anelectronic watermark is inserted, or transmitted to a printer enginethrough a color conversion process and a pseudo-gradation process to beused as an on-paper image including the electronic watermark. Here,either cases can be achieved by the same process, whereby versatility isvery high.

The present embodiment is explained as above, that is, the periodicityto be added to an image signal is selected according to whether apredetermined bit of additional information is “1” or “0”. In case ofseparation (extraction), the additional information is discriminatedbased on the relative comparison of the power values, whereby theabsolute power value by the specific band as shown in, e.g., JapanesePatent Application Laid-Open No. 7-123244 is unnecessary. That is, inthe conventional technique that the absolute value of the power of thespecific band is compared with the absolute value of the predeterminedthreshold, adverse effects due to various deterioration steps such asthe influence of the pseudo-gradation process, the influence of noiseson the paper, and the like become the problem. However, in the method ofperforming the relative comparison according to the present invention,the deterioration uniformly and equally occurs in each target band,whereby it is possible to reduce the above adverse effects in theconventional technique.

In the present embodiment, the additional information multiplexingapparatus and the additional information separation apparatus areexplained as above. However, the present invention is not limited tosuch a combination of the additional information multiplexing apparatusand the additional information separation apparatus. Moreover, as theseparation method of the separation apparatus, there is a method ofdecoding, without using the orthogonal transformation, the informationby using a band-pass filter.

Third Embodiment

FIG. 10 is a block diagram showing the structure of an additionalinformation multiplexing apparatus according to the third embodiment.

In the present embodiment, the various blocks shown in the secondembodiment of FIG. 9 are classified into two kinds of blocks, i.e., aprocessing block for achieving the multiplexing of additionalinformation and an image processing block depending on a printer enginecharacteristic. Here, the present embodiment is structured to controlthe processing block according to application software and control theimage processing block according to a printer driver.

In FIG. 10, numeral 1000 denotes application software. In theapplication software 1000, image information is input through an inputterminal 100, additional information is input through an input terminal101, the image information and the additional information aremultiplexed through a series of multiplexing processes, and multiplexeddata is output to an output terminal 1001.

The multiplexed data output through the output terminal 1001 is onceconverted into predetermined-format data and then stored in a storageapparatus on a computer as an electronic file, or the output multiplexeddata is directly transmitted to a printer driver 1002 as it is. Themultiplexed data stored as the electronic file can be used for otherapplication software to create documents or circulated on the Internet,as well as ordinary image information.

On the other hand, in the printer driver 1002, the multiplexed data isinput from the application software 1000 or other application softwarethrough an input terminal 1003. Moreover, in the printer driver 1002,the input data is processed by a color conversion unit 2000 and apseudo-gradation processing unit 207 which perform image processesinherent in a connected printer, and then output to the printer throughan output terminal 1004, whereby the image data is printed irrespectiveof whether the multiplexed data.

That is, according to the present embodiment, the processes to achievethe multiplexing are completed in the application software, whereby itis possible to achieve the multiplexing process which does not depend onthe characteristic inherent in the printer engine. For example, in theabove embodiment shown in FIG. 2, the multiplexing process is performedafter the color conversion process depending on the characteristic ofthe printer engine, whereby it is necessary to design the parameters forthe multiplexing process optimized for the characteristic of the inkcolor inherent in the printer engine. As a result, it is necessary todesign, for each apparatus, the multiplexing parameters depending on thekind of apparatus in proportion to the number of printers achieving themultiplexing process, whereby a load of design increases.

On the other hand, according to the present embodiment, the multiplexingprocess is completely separated from the process inherent in the printerdevice. Thus, it is possible to create the printed image of themultiplexed data from any printer irrespective of whether themultiplexing process is performed by the printer driver, as long as theapplication software achieving the multiplexing process is used.

For example, with respect to the image data multiplexed by theapplication software, a user who has plural printers can always printthe same multiplexed image data even if he arbitrarily changes theprinter and the device driver of this printer.

OTHER EMBODIMENTS

The present invention is applicable to a system composed of pluralapparatuses (e.g., a host computer, an interface apparatus, a reader, aprinter and the like) or to a single apparatus (e.g., a copying machine,a facsimile apparatus or the like).

Moreover, it is needless to say that the object of the present inventioncan be achieved in a case where a storage medium (or a recording medium)storing the program codes of software to realize the functions of theabove embodiments is supplied to a system or an apparatus and then acomputer (or CPU or MPU) in the system or the apparatus reads andexecutes the program codes stored in the storage medium. In this case,the program codes themselves read from the storage medium realize thefunctions of the above embodiments, whereby the storage medium storingthese program codes constitutes the present invention. Moreover, it isneedless to say that the present invention also includes not only a casewhere the functions of the above embodiments are realized by executingthe program codes read by the computer, but also a case where an OS(operating system) or the like functioning on the computer executes apart or all of the actual process according to the instructions of theprogram codes, whereby the functions of the above embodiments areachieved by that process.

Moreover, it is needless to say that the present invention includes acase where the program codes read from the storage medium are oncewritten in a memory provided in a function expansion card inserted inthe computer or a function expansion unit connected to the computer, andthen a CPU or the like provided in the function expansion card or thefunction expansion unit executes a part or all of the actual processaccording to the instructions of the program codes, whereby thefunctions of the above embodiments are achieved by that process.

As explained above, according to the present invention, the differentperiodicity is selected according to the additional information and thusthe additional information is actually embedded, the image qualitydeterioration or the like due to the embedding of the additionalinformation is not visibly recognized, and it is possible to embed theadditional information so that the embedded information can be easilyextracted from the paper. storage medium.

Moreover, the additional information can be easily multiplexed in theimage information, whereby it is possible to provide service andapplication for embedding audio information or secret information in theimage information. Moreover, it is possible to control an illegalforgery act for bank notes, stamps, valuable securities and the like,and it is also possible to prevent a copyright infringement of the imageinformation.

1. An image processing apparatus which embeds predetermined informationin an image, comprising: input means for inputting the image; divisionmeans for dividing the input image into plural image regions, therespective image regions having a same size; periodicity generationmeans for generating plural different periodicities, the pluraldifferent periodicities being generated in different directions;addition means for adding a positive predetermined value or a negativepredetermined value to a pixel value of each pixel in the image regiondivided by said division means, on the basis of the periodicity; andselection means for selecting the periodicity for the addition fromamong the plural periodicities, in accordance with the predeterminedinformation, as a result of the addition by said addition means, plurallines which are composed of plural pixels to which the positivepredetermined value and the negative predetermined value are added andwhich are based on the respective directions of periods are formedwithin the respective image regions divided by said division means. 2.An apparatus according to claim 1, wherein the plural periodicities areobtained as sets of the horizontal period and the vertical period whichhave been mutually replaced.
 3. An apparatus according to claim 1,wherein said addition means adds the predetermined value to a densitysignal according to each pixel.
 4. An apparatus according to claim 1,wherein the periodicities are generated by using plural differenttables.
 5. An image processing apparatus which embeds predeterminedinformation in an image, comprising: input means for inputting theimage; division means for dividing the input image into plural imageregions, the respective image regions having a same size; periodicitygeneration means for generating plural different periodicities, theplural different periodicities being generated in different directions;addition means for adding a positive predetermined value or a negativepredetermined value to a pixel value of each pixel in the image regiondivided by said division means, on the basis of the periodicity;selection means for selecting the periodicity for the addition fromamong the plural periodicities, in accordance with the predeterminedinformation; conversion means for converting each pixel into a densitysignal for each coloring material; and recording means for recording thedensity signal after the conversion by said conversion means, on aprinting medium, wherein said addition means performs the additionprocess to the information before the conversion by said conversionmeans, and wherein, as a result of the addition by said addition means,plural lines which are composed of plural pixels to which the positivepredetermined value and the negative predetermined value are added andwhich are based on the respective directions of periods are formedwithin the respective image regions divided by said division means. 6.An apparatus according to claim 5, wherein the process by each of saidinput means, said division means, said periodicity generation means,said addition means and said selection means is executed in applicationsoftware, and the process by each of said conversion means and saidrecording means is executed in a printer driver.
 7. An image processingmethod of embedding predetermined information in an image, comprising:an input step of inputting the image; a division step of dividing theinput image into plural image regions, the respective image regionshaving a same size; a periodicity generation step of generating pluraldifferent periodicities, the plural different periodicities beinggenerated in different directions; an addition step of adding a positivepredetermined value or a negative predetermined value to a pixel valueof each pixel in the image region divided in said division step, on thebasis of the periodicity; and a selection step of selecting theperiodicity for the addition from among the plural periodicities, inaccordance with the predetermined information, as a result of theaddition by said addition means, plural lines which are composed ofplural pixels to which the positive predetermined value and the negativepredetermined value are added and which are based on the respectivedirections of periods are formed within the respective image regionsdivided by said division means.
 8. An image processing method ofembedding predetermined information in an image, comprising: an inputstep of inputting the image; a division step of dividing the input imageinto plural image regions, the respective image regions having a samesize; a periodicity generation step of generating plural differentperiodicities, the plural different periodicities being generated indifferent directions; an addition step of adding a positivepredetermined value or a negative predetermined value to a pixel valueof each pixel in the image region divided in said division step, on thebasis of the periodicity; a selection step of selecting the periodicityfor the addition from among the plural periodicities, in accordance withthe predetermined information; a conversion step of converting eachpixel into a density signal for each coloring material; and a recordingstep of recording the density signal after the conversion in saidconversion step, on a printing medium, wherein the addition process insaid addition step is performed to the information before the conversionin said conversion step, and wherein, as result of the addition by saidaddition means, plural lines which are composed of plural pixels towhich the positive predetermined value and the negative predeterminedvalue are added and which are based on the respective directions ofperiods are formed within the respective image regions divided by saiddivision means.
 9. A program embodied in a computer-readable storagemedium, which is executed on a computer to achieve an image processingmethod of embedding predetermined information in an image, said methodcomprising: an input step of inputting the image; a division step ofdividing the input image into plural image regions, the respective imageregions having a same size; a periodicity generation step of generatingplural different periodicities, the plural different periodicities beinggenerated in different directions; an addition step of adding a positivepredetermined value or a negative predetermined value to a pixel valueof each pixel in the image region divided in said division step, on thebasis of the periodicity; and a selection step of selecting theperiodicity for the addition from among the plural periodicities, inaccordance with the predetermined information, wherein, as a result ofthe addition by said addition means, plural lines which are composed ofplural pixels to which the positive predetermined value and the negativepredetermined value are added and which are based on the respectivedirections of periods are formed within the respective image regionsdivided by said division means.
 10. A program embodied in acomputer-readable storage medium, which is executed on a computer toachieve an image processing method of embedding predeterminedinformation in an image, said method comprising: an input step ofinputting the image; a division step of dividing the input image intoplural image regions, the respective image regions having a same size; aperiodicity generation step of generating plural differentperiodicities, the plural different periodicities being generated indifferent directions; an addition step of adding a positivepredetermined value or a negative predetermined value to a pixel valueof each pixel in the image region divided in said division step, on thebasis of the periodicity; a selection step of selecting the periodicityfor the addition from among the plural periodicities, in accordance withthe predetermined information; a conversion step of converting eachpixel into a density signal for each coloring material; and a recordingstep of recording the density signal after the conversion in saidconversion step, on a printing medium, wherein the addition process insaid addition step is performed to the information before the conversionin said conversion step, and wherein, as a result of the addition bysaid addition means, plural lines which are composed of plural pixels towhich the positive predetermined value and the negative predeterminedvalue are added and which are based on the respective directions ofperiods are formed within the respective image regions divided by saiddivision means.
 11. A computer-readable recording medium having recordedthereon a program to be executed on a computer to achieve an imageprocessing method of embedding predetermined information in an image,said method comprising: an input step of inputting the image; a divisionstep of dividing the input image into plural image regions, therespective image regions having a same size; a periodicity generationstep of generating plural different periodicities, the plural differentperiodicities being generated in different directions; an addition stepof adding a positive predetermined value or a negative predeterminedvalue to a pixel value of each pixel in the image region divided in saiddivision step, on the basis of the periodicity; and a selection step ofselecting the periodicity for the addition from among the pluralperiodicities, in accordance with the predetermined information,wherein, as a result of the addition by said addition means, plurallines which are composed of plural pixels to which the positivepredetermined value and the negative predetermined value are added andwhich are based on the respective directions of periods are formedwithin the respective image regions divided by said division means. 12.A computer-readable recording medium which records thereon a program tobe executed on a computer to achieve an image processing method ofembedding predetermined information in an image, said method comprising:an input step of inputting the image; a division step of dividing theinput image into plural image regions, the respective image regionshaving a same size; a periodicity generation step of generating pluraldifferent periodicities, the plural different periodicities beinggenerated in different directions; an addition step of adding a positivepredetermined value or a negative predetermined value to a pixel valueof each pixel in the image region divided in said division step, on thebasis of the periodicity; a selection step of selecting the periodicityfor the addition from among the plural periodicities, in accordance withthe predetermined information; a conversion step of converting eachpixel into a density signal for each coloring material; and a recordingstep of recording the density signal after the conversion in saidconversion step, on a printing medium, wherein the addition process insaid addition step is performed to the information before the conversionin said conversion step, and wherein, as a result of the addition bysaid addition means, plural lines which are composed of plural pixels towhich the positive predetermined value and the negative predeterminedvalue are added and which are based on the respective directions ofperiods are formed within the respective image regions divided by saiddivision means.